Elevator control system



Nov. 15, 1949 A. PINTO ELEVATOR CONTROL SYSTEM UHS 2 Sheets-Sheet l INVENTOD ATTOQNEY Patented Nov. 1 5 1949 ELEVATOR; CONTROL SYSTEM aAnthony-Binto, New Rochelle, N. Y.,. assignornto .Otis Elevator. Company; New, York; N ;Y., a corv.pora'tion of Newj'Jersey Application November 25,- 19417 if SerialrN 0; {787;953

.llcClaims. ll The-.zinvention relates to. electric elevators and especially to controlling.thelstoppingtofl the. ele- 1 yatoncar; so,as:to.obtain accurate.- stpps.

L'Therezare various. factors in elevator operation .-which;.affectitheeaccuracy,of stopping; of thecar -:-.at;.=the;iand.in s. amongawhich are the. load carriedizbyzathe car, :the KdireCt -QI]. of travel of the car and; its position in the hoistway and, friction. .QIn traction machine installations, the. elevator 17211115 counterbalancedpy. a. counterweieht,.-usug ally ;-overbalanced; atorty per cent- 50f; the :ratedcar I ;1Qad;=.and the car-and; counterweight, 13/16, suspended.byrhoistine'ropes;which extend upwardly and around. a .hoistingzsheave, ,driven by. the hoisting :motor. 3111-3314011. installations @when therezis a nheavy :load inst-he, carloverbalancing the counteriweigh \iwiih'. 1 p ;.direction;;.0f car :movement the 3hoisting;motorisprequiredtm lift the car;:wherezfiSsWith down;.direction 0f;car movementgravity aefiectstheymoyement. =r .Conversely,-. when; the: car

is empty so that the counterweight overbalances :ibhecan with upjdirection otcar movement gravdinetteetsthe movement, whereas with, down:.di-

rection of :car:;m0vement the hoisting :motor: is

cquired to lift;theecounterweight. 'Duetoithe -;variations in the loadin the-car and the factxthat illhe directionofcarlmovementmaybe upon-down itis diflicult to effect an accurate stop'unless-some form of. load compensation is provided. The.load

carried.-by the car theldirection .of, cartravel.

sthe positiomot the; car in: the hoistway and; incitiong a1l affect the .net load .on thechoistii 1g mo- -..-tor and. thisnet .load maybe utilizedasa measunrement. :for sdetermining the v. compensation to -efiectan accurate stop.

":The: objecttof. thex-inventionpia to provide; simifp and inexpensive apparatus for compensating for the load on an elevator hoisting motor in stop- ;ping thecar.

' The inventioninvolves chargingacondenser in .-.accorda-nce .with; the. load; on the: hoisting; motor and gutilizi fl thei condenser charge-t0, control the :1 stoppingloperations so as-to obtain accurate stops.

In. the -par-ticu1ar.,arrangement. which=will be: de-

determined by the charge on the condenser.'

.whichin turn is :determined by the netload on ,..theihoiszting .motor.

JIhe zinventionis.especially:applicable to-eleva- -tor installations :employing 1 single 1 speed ..-po lyphasei alternating, current .hoisting -..motors.= andt Cil s such. 'an application hwillube described. .As, al plied; to.- such an Zinsta'llation; load .determining apparatus ,i is. illustrated. in which the secondary v.voltage of .a,.si ng 1e .phasecurrent transformer having its primaryinvserles. with one ofthe sup- .ply lines is combined with,,a..fixed.voltagei taken from. the lines. .The, condenser..andflthencoil .of .the .controlled switch are connected. through, a rectifier.,.to' .besubject. to..the vector. sum .of.lt hese two. voltages. .The. value of this. resultant v'o'ltvage.varieswiththe net load on the. hoistingmotor so. that the charge on. the condenser. and J therefore the. .time.,.of. dropping out ,of the. controi switch. after. thev motor .circuits .are broken; is -inaccordance with the load on the motor.

a Aseneral idea. ofntheinvention; the mode (of carrying itout whichisatpresent preferred, and various features-land advantages thereof willibe gainedhfrommtheabovestatements. V'Other featuresandadvantages. of..the invention will be apv. .parer1t .from the J following description and appended claims.

.Inthe. drawings: vFigure 1- ishalsimplified :.wiring diagram in ffacrossethe-line formuof an elevator control system. chosen to illustrate. the principles ,ofijthe invention and Figure 181 is; a'. .keyJsheet' for. Figure. 1. showing the electromagnetic switches in spindle form with the, contacts .andcoils. arranged on the. spin- -.-.d1es inhorizontal alignment .with the, correspondhingcontactsandcoilsin1.the wiring dia ram.

For illustrating the principles of. the invention ..a..system. ofoelevatoro control. has; been. -illustrated in which the slow down andistopping ofjthe'car ,atflthe Yariousfioorsis automatic. There are varioustypes oi. elevator, control. of. this character, the type illustrate'd'b'eingknown as collective push button control. A selectivezcollective push button-control system has: been illustrated in which the :pressing of:arpushr-button either in the car or at-a landing 'starts the-car. The car is slowed down and 'stoppedzatlandings for which push buttons corresponding .toxthe direction of car travel have been -pressed; the car being automatically restarted:after:- each=stop so long as push buttons -remain -toi be"responded to.

Push button COIltIOlfCiICUi'tS 'f0r 0n1ynfOlll floors are illustrated. -A pushzbutton is provided in the car for each of thef-floors. Also, a push button is provided at the first and sfourth floors: and anup push -button and a downapush button mare providedi both: at {the :second and at the third fioors. The push bu-ttons: in-"the. car are designated in accordance withithehulocation and the floor for which theyxareprovided. .For example, CB3 designates the third'ifloorcar button. Pus -buttons: atthe.landingsaredesignated .dnaaccordance with..the.floor and them-direction.

3 For example, ZUI-I designates the up second floor hall button.

The push buttons act through floor relays to control the operation of the car. The floor relays are designated similarly to their controlling push buttons, the car button floor relays being designated C and the hall button floor relays being designated U or D depending upon whether they are provided for up push buttons or down push buttons. The floor relays, when operated, remain in operated condition as by latching, thereby permitting the push buttons to be released. When the call is answered, the floor relay is reset. Various forms of such floor relays may be utilized.

Thefioor relays are arranged to act through direction mechanism on a floor controller to control the direction of travel of the elevator car. This floor controller is also utiilzed in the form of control illustrated to control the stopping of the car. The particular parts of the floor controller employed in the system illustrated have been diagrammatically indicated in the wiring diagram. The direction mechanism comprises a plurality of stationary direction switches, one for each floor, designated FHI, FHZ, Fl-I3 and FHA for the first, second, third and fourth floors respectively, and a direction cam of three sections designated CU, CM and CD carried by the floor controller crosshead. The floor controller has stationary contacts arranged in three columns under the designations CAC, UHC and DHC, those in column CAC being rendered alive by the car buttons, those in column UHC by the up hall buttons and those in columns DHC by the down hall buttons. Brushes are carried by the floor controller crosshead for engaging these contacts to pick up calls, these brushes being designated U08 and DCS for contacts CAC, UHS for contacts UHC, and DI-IS for contacts DHC. Reset brushes are also carried by the crosshead for engaging the stationary contacts to reset the calls, these brushes being designated CAR, UHR and DHR for contacts CAC, UHC and DHC respectively. Up stop switches UMSI and UMSZ and down stop switches DMSI and DMSZ are carried by the crosshead and are operated by stationary cams as the car arrives at the respective floors in the direction forwhich the stop switches are provided.

The electromagnetic switches employed in the control system have been designated as follows:

A, Up reversing switch AU, Up reversing switch relay B, Down reversing switch BD, Down reversing switch relay CC, Car button relay CT, Reverse resistance relay DC, Door close switch DL, Auxiliary door relay DO, Door open switch DR, Door relay DZ, Door re-open relay GH, Auxiliary door close relay HO, Hall re-open relay K, Accelerating switch LD, Down auxiliary reversing switch relay LU, Up auxiliary reversing switch relay P, Main line switch Q, Load switch S, Stopping relay 2, Time relay Throughout the description which follows, these letters will be applied to the coils of the above designated switches. Also, with reference numerals appendedthereto they will be applied to the contacts of these switches as for example Al.

The supply mains of the polyphase alternating current source of supply are designated I, II and III. KS is a triple-pole knife switch for connecting the system to the supply mains. A polyphase rectifier RE is utilized to provide direct current derived from the alternating cur rent supply mains for operating the floor relays and certain of the electromagnetic switches. BR is the release coil of the electromechanical brake. BRRl andBRRZ are resistances for controlling the energization of the brake release coil. CBR is a condenser connected across the brake release coil. REB is a rectifier in the circuit for brake discharge resistance BRRZ.

The hoisting motor is a polyphase alternating current squirrel cage induction motor. The stator windings of the motor are designated MOI, M02 and M03 while the rotor is designated MOR. SRl, SR2 and SR3 are resistances in circuit with the stator windings of the hoisting motor.

The gate contacts are designated GS while the door contacts are designated DS. Both the car gate and the hatchway doors are operated by a motor carried by the elevator car, as for example as disclosed in the patent to Norton et al., Number 1,950,150, granted March 6, 1934. The door operating motor is a polyphase alternating current squirrel cage induction motor. The stator windings of this motor are designated DMl, DMZ and DM3 while the rotor is designated DMR. DSR! and DSR3 designate resistances in circuit with the stator windings of the door operating motor.

An emergency stop switch ES is provided in the car. The contacts of the various safety devices are indicated by the legend safeties." Terminal limit switches are designated UTLI and DTLI. 'Limit switches operated by the door operating mechanism are designated DOLI, DCLl, DCLZ and DOL2. DZL is a door zone limit switch carried by the car and closed by cams in the hatchway, one at each floor.

TRQ designates the transformer utilized in.

determining the load on the elevator motor. CQ is a condenser connected across the coil of load switch Q while REQI and REQZ are rectifiers in the circuit from the transformer secondary to the coil of switch Q and condenser CQ. QRI, QR QR3, QRG, QR5 and QRS are resistances in the circuits.

Other resistances employed in the control system are designated RI, R2, R3, R4, R5, R6, R1, R8, R9 and RID. Other condensers utilized are designated COI and C02. The electromagnetic switchesare illustrated in deenergized position. Also, all latching switches are illustrated in reset condition.

Before describing the operation of the load determining apparatus and the control exercised thereby in stopping the car, operation of the car in response to the push buttons will be described.

Assume that the car is idle at the second floor, the floor controller being illustrated in accordance with this assumption. As the car is idle, the second floor hatchway door and car gate are closed, thus door contacts DS and gate contacts GS are engaged. V

Assume now that an intending passenger at the third floor pressed up third floor hall button 3UI-I. This completes the circuit for the operating coil of up third floor relay 3U. The third floor relay operates to engage contacts (WI and engages contacts- AU I, =-AU2 and AU l and-separates contacts -AU3. Up reversingswitch-A, upon'operation, engages contacts -Al A2, -A3 arid A6 and separates contacts A4 and A5. 7 Contacts "A4 are interlock contacts in the circuit for the *coils of down reversing switch relay BD and down reversing switch B. Contacts AU3 separate to I render down brushes DHS and D08 ineffective -for up car travel. Contacts AU4 completea circuit for the coil of up auxiliary reversing switch relay LU. Contacts At;v complete the circuit. for;

.-..the operating coilof stopping relay S,.the circuit being through contacts vDZ3 and Z2,. operating coil of relay Sand contacts A6.

.Relay LU, upon operation, separates contacts LU| and engages contacts LUZ. operation, engages contacts SI, S2 and S3. The 1 separation of contacts LUl.renders reset brush DHR ineffective for .up car travel. The engagementof contacts LUZ and of contacts S2completes a circuit for the coils of main line switch P and auxiliary door relay DL, this circuit being through these coils in parallel, contacts LUZ, contacts S2, door contacts DS and gate oontactsGS.

. Switch P, upon operation, engages contacts. Pl, P2, P3 and P4 and separates contacts P5.

engagement of contacts PI and P2 together with the engagement of contacts AI and A2 completes the circuit for the stator windings of the hoisting motor for a phase rotation of applied voltage for updirection of car travel. At the same time contacts P3 and P4 and contacts A3 complete the circuit for the brake release coil BR through contacts BRI. As a result the brake is released and the car is started-in the up direction. As the brake releases, it separates brake switch contactsBRI to insertresistance BRRI in series .with the brake release coil. Rectifier REB blocks the flow of current through resistance BRRZ when the brake circuit is established. Thus this resistance is in eifect taken 01f the line, being of a low value. Also, this prevents. the application of the brake upon. the insertion of cooling resistance BRRI which might otherwise occur due to the low value of resistance BRR2.

'Relay DL, upon operation, engages contacts FDLI and DL3 and separates contacts DLZ. The engagement of contacts DLI complet-esa circuit for the coil of time relay Z. The engagement of contacts DLS completes a circuit for the coil ofdoor relay DR.

Time relay Z, upon operation, separates contacts Zl and Z2. The separation of Zl is without efiect as they are now by-passed by contacts AUZ. The separation of contacts Z2 breaks the circuit for the operating coil of stopping relay S. This relay is of the same type as the floor relays, remaining in operating condition when the circuit for its operating coil is broken.

:Relay DR, upon operation, engages contacts :DRI, DR2 and DR3. The engagement of contacts 1 DR3 establishes a-selfholding circuit -.for thecoil 'of relay DR. Contacts DL2 separate before con- ,tacts DBL-engage, thereby preventing the energization of the coils of switches DO- andDZ.

The: engagement of contactsrP4..and contacts Relay S, upon The P;

A3 a'lso coinpletes a circuitl for: theicoilioflaccelerating switch K. Thisswitch::does:.notzoperate immediately the circuit .for its uoperating coiliis completed,- being delayed asbya-dashpot. ZUpon operation itcngages contacts K I... and K2v to: short circuit resistances SRLI: SR2. and SR3.:inccircuit -with' the stator windingsa-ofcthe; hoistingcmotor to increase the torque for: iullrrspeedc: operation. As the carleaves ithesecond floonup stop. switches cuits for thecoils .of. the relays AU and; DL and switches Azand. P.

'UMS l a andUMSZ: close icompletingzz-holding- :cir-

:As the carinears the third floor, :up. brushes U CS. and U HSengage' stationary; contacts SCAC3 relay-is operated, the. engagement .of bruslrUHS with contacts.UHC3:completes a circuit for the :resetcoil of stopping relay S:-,through.--resistance 3. R6,. contactsrBDl brush UHS,: contact. UHC3; re-

atactseilUZ. .Z'Phe voltage appliedtothe reset. coil of thefio-or relayeis: not sufficienttoresehthis set coil 3U .of: .theup thirdsfloor: relay .and ,con-

relay. This voltage, however, is;-sufiicient.-to

cause; the: resetting, of the stopping relay. .=As a energizing circuit for the coils of main line switch result. contacts: S2 .separate to break .the yinitial P and :auxiliary. ;door; relay DL. v.fl hese-coils'are maintained energized, =howeve r,-- through :up stop switch UMSZ. .As the car-continues its: move- ..ment,- third floor direction. switch 'FI-I3,-moves.-ofi

.upcam section CU,-;breaking; the. initiaLenergizingcircuit for: the. coils of..up reversing switch A and up reversing 'switch relay'AU. These-coils are broken .andtthe brake release coil BRisdeenergized and thebrake applied to-bring the-car :to' a stop at. the. third floor. -contacts'A3 and P4.as the car-is brought toastop Thegseparation '-.of

breaks thecircuit for the. coilof-. accelerating switch K while the separation of contacts AU4 breaks the circuit-for the coil. of. relay-LU.

.Auxiliary -.door. relay DL,: upondropping out,

separates contacts DLI. and DL3; and engagescon- .-tacts DL2. -The engagement sOfcontacts.- DLZ completes a circuit throughdoonzone limit switch ..to open, limit switch DCLZ closes to completegthe circuit for the coilof auxiliarydoor close relay DZL-now'closed and contactsDRl .for the coils=of door open switch DO and door re-open relayDZ.

The door ,openswitch DO. engages contacts .DOI

and; D02: to energize the. stator. windings .of. .the

door operating motor to open thedoor/and. gate.

The door re.-open relay. DZengages contacts DZ2 to by-pass contacts DL l tomaintain the coil of time relay Z energized. As the door and gate start GH. Relay GH engages contacts GH2 .which,-to-

. openrelayl-IO. .Thus, with contacts P5..engaged and brush UHRin-engagementwith the. third .gether with the-engagement. of contacts .DZI, complete a by-pass circuit forthe coil of hall refloor stationary. contactUHG3, a. circuit is completed which causes the application of sufiicient voltage to reset coil. of the up. third floor relay. to

-. cause this relay tobe reset.

=As the door-.andgate reachopen position, limit of idoorzopen switch bQzand' 'the ppeningzoi :Iimit switch 1501.2 breaks the circuit for the coil of door relay DR, causing these switches to drop out. The droping out of switch DO breaks the circuit for the door operating motor. The dropping out of relay DR breaks the circuit for the coil of door re-open relay DZ, causing this relay to drop out. The dropping out of switch DO breaks the circuit for the coil of time relay Z. This relay is delayed in dropping out b the discharge of condenser CO1 and acts to prevent reestablishment of starting circuits and thus to enable the passenger to enter the car. Under the conditions assumed it also provides time for the passenger to press a car button for his desired destination and thus determine the direction of car travel. When the time interval of this relay has expired, contacts Zl reengage rendering the hall buttons effective to control direction and contacts Z2 engage to establish a circuit for the coil of door close switch DC. This switch engages contacts DC! and D02 to establish a circuit for the stator windings of the door operating motor for effecting closing of the door and gate. 7

The car is started in the down direction in response to the pressing of a button for a fioor below the car. scribe this operation as it is believed it will be understood from the above description of starting the car in the up direction. For starting the car in the down direction down reversing switch relay BD, down auxiliary reversing switch relay LD and down reversing switch B are operated instead of relays AU and LU and switch A.

The car is stopped during downward travel in response to down hall buttons that have been pressed, stopping relay S being reset in response to engagement of brush DHS with the stationary contact DI-IC for the floor for which the down hall button has been pressed. Stops in response to car buttons are made during either direction of travel, brush UCS effecting the the reset of the stoppping switch for up travel and brush DCS effecting the reset of the stopping switch for down car travel. In case buttons have been pressed for two or more floors ahead of the car in the direction of car travel, for up car travel for example, coils of switches AU and A are maintained operated by the operated floor relays until the highest floor for which a button has been pressed is reached. If during travel of the car in the up direction for example, nopush button has been pressed for a higher floor, a stop may be made in response to a down button. In this case the stopping relay is reset by the reengagement of contacts A as switch UMSI opens thereby enabling the opening of switch UMSZ to deenergize the coils of switches P and DL.

In stopping the car at the landings, the action of the brake is controlled in such manner as to compensate for the load on the hoisting motor to cause the stops to be accurately made. This con- It is not believed necessary to deinduced in the secondary of transformer varies with load. This transformer secondary voltage is combined with a voltage taken off the lines, the value and phase of which remains fixed. As the phase relationship of these voltage components varies with load their vector sum varies with load. This vector sum of these combined voltage is applied to the condenser so that the charge on the condenser is in accordance with the load on the motor. Rectifier REQI and REQZ are provided in the circuit to the condenser to cause the current supplied to the condenser to be unidirectional. V

The transformer utilized has a closed core. This type is preferred as it minimizes the size of transformer used. Loading resistances QR3 and QR l are connected across the secondary or the transformer. Due to the type of transformer used and the amount of loading resistance employed, the secondary voltage of the transformer from its terminal connected to line III to its other terminal is in phase with the transformer primary current. The fixed voltage component utilized is that from line III to adjustable point V on resistance QRI. This fixed voltage vector is 180 out of phase with the current in the primary of the transformer at no load on the motor. Thus, these voltage vectors at no load on the motor are in phase opposition and their vector trol of the brake is effected through load switch motors does not vary a great deal with changes in load, the phase of this current with respect to that of the applied voltage, i. e., the power factor, does vary considerably with load. Thus, in the arrangement illustrated, the phase of the voltage sum of the combined voltages increases.

sum is a minimum. As the load on the motor increases, the lag of the primary current with respect to the voltage of line II to neutral decreases and thus the lag of the transformer secondary voltage decreases with a result that the vector This vector sum of combined fixed and transformer secondary voltages provides an accurate measurement of the load on the motor.

It is preferred that both these voltage components be adjustable. This adjustment for the line voltage component is provided by the slider V on the voltage divider resistance QRI. Adjustable resistance QR l provides this adjustment for the transformer secondary voltage. For certain geared installations of about feet per minute, it has been found that a satisfactory adjustment is to have the voltage vectors of about equal value for empty car up. For such adjustment a switch Q is provided with a hold-in voltage near the resultant voltage obtained with the empty car up setting and further adjustment is made so that the resultant voltage equals the hold-in voltage value of the relay.

With such an arrangement, switch Q is always operated in starting the car. The condenser is recharged upon each starting operation, the ultimate charge being determined just before the motor circuits are broken as a stop is to be made. When the motor circuits are broken the condenser starts to discharge. The motor circuits and the brake circuit are broken at a fixed distance from the landings, preferably the same for each direction of travel. If during operation the load on the motor is below that for empty car up, for example full load down, when steady state conditions are reached there will be insufficient voltage applied to the condenser and the coil of switch Q and this switch will drop out. Under such load conditions, the brake discharge resistance BRRZ is disconnected from across the brake release coil before the brake release coil circuit is broken 'so that when this circuit is broken in stopping the car the brake is immediately applied. "I'he distance of the car from the floor when the motor and brake circuits are broken is set so that for such overhauling load conditions the brake is able to bring the car to a stop at the floor level.- If the load is at empty car up, load switch Q is held until the motor cir= cults are broken, thereby providing a slight time element in the disconnection of resistance BRRI. For greater loads on the motor the charge on the condenser is greater. Under such load conditions, the switch Q is held in operated condition by the charge on the condenser aiter the motor circuits are broken and the extent of the period during which switch Q is held in by the action of the condenser is greater the greater the load. Thus. the greater the load on the motor, the longer the brake discharge resistance is maintained con nected across the brake release coil and the closer the car arrives to the floor before the brake is applied.- For full load on the motor, the brake discharge resistance is maintained connected substantiaily until the car reaches the floor. Thus the action of the brake is controlled to give accugate stops under the various diiferent load condiions.

The value of brake discharge resistance BRRZ is such as to be capable of holding the brake off tor the full stopping distance if allowed to remain connected. However, it will allow the brake to drop out without considerable overtravel of the car, thereby assuring the stopping of the car in case the contacts of switch Q fail to open. The discharge time of condenser CQ is determined by resistances QR2 and QRB, resistance QR5 being adjustable to enable the discharge time to be varied. Resistance QR3 serves as a loading resistance for the transformer. This not onl prevents damage to the transformer but also obviates the possibility of injur to persons touching the secondary terminals. Resistance QRB in conjunction with condenser CQ acts as a filter to suppress hi h peak voltage surges across the coil of switch Q when the motor is started.

While the invention is particularly applicable to slow speed installations, it is to be understood that it is also applicable to higher speed installations. It is also to be understood that various changes may be made in the particular arrangemerit shown and specifically described. The load responsive apparatus may be utilized to control the point at which the motor circuits and brake circuit are broker or it may be utilized for other purposes than controlling the stopping of an olevator car. It is preferred to connect the load determining apparatus as illustrated, but other arrangements may be employed, as for example an arrangement in which the transformer secondary winding voltage is combined with some other voltage taken on: the supply lines to vary the resultant voltage in accordance with the load on the motor. In this connection, resistance QR! may be connected at one end to an adjustable point on a voltage divider resistance connected across supply line II and the supply line to which such end is shown connected in Figure 1. This enables adjustment of the phase of the line voltage which is combined with the secondary voltage. Such arrangement would be particularly advantageous for certain installations where due to inherent characteristics adjustment would be desirable for compensating for intermediate loads. Other load determining arrangements may be utilized for charging the condenser in accordance with the load on the motor. Also, the charge on the condenser may be utilized in other ways for controlling the stopping of the car.

Although the invention has been described as applied to a three phase alternating current elevator installation, it is applicable to installations of other numbers of phases. Also, the invention may be applied to installations in which a direct current hoisting motor is employed with the condenser charged in accordance with the load on the motor. Although a collective push button control system has been described, it is to be understood that the invention is applicable to other forms of push button control and to systems controlled in other ways such as those in which the starting of the car is under the control of an attendant in the car with slow down controlled by passengers and intending passengers themselves, those in which both starting and slow down are under the control of a car attendant, with the slow down initiated automatically after movement of the control switch in the car to a certain position, or those in which both starting and slow down are controlled directly by the car attendant.

Thus as many changes may be made without departing from the scope of the invention and as the invention has many applications, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In combination; an electric motor subject to Varying loads; a source of current for said motor; a condenser; means for charging said condenser in accordance with the load on the motor; and a switch controlled by the-discharge of said condenser so as to drop out in a time after the discontinuance of the charging of said condenser determined by the load on the motor.

2. In combination; an elevator car; a hoisting motor therefor; a source of current for said hoisting motor; a condenser; means for charging said condenser in accordance with the load on said motor; means for stopping the car at a landing; and means controlled by the discharge of said condenser for controlling said stopping means to compensate for the load in the car.

3. In combination; an elevator car adapted to serve a. plurality of landings; a hoisting motor therefor; a source of current for said hoisting motor; a condenser; means for charging said condenser in accordance with the load on said motor; means for stopping the car; and means rendered subject to the discharge of said condenser in initiating the stopping of the car at any one of said landings for controlling said stopping means to compensate for the load in the car so as to make an accurate stop at that landing.

4. In combination; an elevator car adapted to serve a plurality of landings; an alternating current hoisting motor therefor; a source of alternating current for said motor; a condenser; means for charging said condenser an amount determined by the vector sum of a voltage of said source and a voltage of a phase determined by the current supplied to said motor; stopping means for said car; and means controlled by the discharge of said condenser incident to the stopping of thecar at any of said landings for causing an accurate stop to be made.

5. In combination; an elevator car adapted to serve a. plurality of landings; an alternating current hoisting motor therefor; a source of alternating current for said motor; a transformer having its primary winding excited in accordance with the current supplied to said motor; a condenser; means for charging said condenser an amount determined by the vector sum of the voltage of the secondary winding of said trans: former and a voltage taken off said source; stopping means for said car; means operable incident to stopping the car at any of said landings to discontinue the charging of said condenser; and means thereafter controlled by the discharge of said condenser for controlling said stopping means to cause an accurate stop to be made.

6. In combination; an elevator car adapted to serve a pluralityof landings; an alternating current hoisting motor therefor; a source of alternating current for said motor; a transformer having its primary winding connected to be subject to the current supplied to said motor; means for vectorially combining a voltage from said source with the voltage of the secondary winding of said transformer; a condenser; means for charging said condenser with unidirectional current derived from said combined voltages; means for stopping the car; means operable at a fixed distance from any of said landings at which a stop is to be made to discontinue the charging of said condenser; and means controlled by the discharge of said condenser after said discontinuance of the charging thereof for controlling said stopping means to cause an accurate stop to be made. I

'7. Load compensating apparatus for an elevator installation in which the elevator car serves a plurality of landings and is driven byan alternating current motor which is connected to an alternating current source for starting and disconnected therefrom for "stopping, said apparatus comprising; a transformer having its primary winding connected to be subject to the current supplied to said motor; means for providing' a fixed voltage taken from said source for vectorially combining with the voltage of the secondary winding of said transformer; a condenser; means for charging said condenser'with unidirectional current derived from said combined voltages; stopping means for said car; means operable at a fixed distance from any of said landings at which a stop is to be made to discontinue the charging of said condenser; and a switch controlled by the discharge of said condenser after said discontinuance of the charging thereof for controlling the operation of said stop ping means to compensate for the load in the car in stopping the car.

8. Load compensating apparatus for an elevator installation in which the elevator car serves a plurality of landings and is driven by a polyphase alternating current induction motor which is connected to a source of polyphase alternating current for starting and disconnected therefrom for stopping, said apparatus comprising; a current transformer having its primary winding connected to be subject to the current supplied to said motor from one phase of said source; means for providing a fixed voltage taken from said source for vectorially combining'with the voltage of the transformer secondary winding to provide a resultant voltage which increases with increase in thenet load on the motor; a condenser; means for causing unidirectional current derived from said combined voltages to be 'supplied to said condenser upon each operation of said car to charge said condenser in accordance with the load on the motor; switching mechanism operable at a fixed distance from any of said landings at which a stop is to be made to dis} connect said motor from said source and to discontinue the charging of said condenser; an electromechanical brake for said motor; and a switch controlled by the discharge of said condenser after said discontinuance of the charging thereof for controlling the application of said brake in stopping the car.

9. Load compensating apparatus for an elevator installation in which the elevator car serves a plurality of landings and is driven by a polyphase alternating current induction motor which is connected to a source of polyphase alternating current for starting and disconnected therefrom for stopping, said apparatus comprising; a single phase current transformer having its primary winding connected in one of the alternating current supply lines in series with said motor; means for providing a voltage from'said source for vectorially combining with the voltage of the transformer secondary winding to provide a resultant voltage which increases with increase in the net load on the motor; a rectifier; a condenser connected with said rectifier in series therewith to be subject to said combined voltages so that upon each operation of said car said condenser is charged with unidirectional current in accordance with the load on the motor; an electromechanical brake for said motor; a switch having an operating coil connected in parallel with said condenser to be operated upon each operation of said car; and switching mechanism operable at a fixed distance from any of said landings at which a stop is to be made to disconnect said motor from said source whereupon the charging of said condenser is discontinued and the condenser discharges into said switch coil to maintain the switch operated for a time determined by the load on the motor; and means operable upon the release of said switch for causing the brake to be applied for stopping the car.

10. Load compensating apparatus for an elevator installation in which the elevator car serves a plurality of landings and is driven by a threephase alternating current induction hoisting motor which is connected to a source of three-phase alternating current for starting and disconnected therefrom for stopping, said apparatus comprising; a single phase current transformer having its primary winding connected in one of the alternating current supply lines in series with said motor; means for providing a fixed voltage from said source substantially equal and opposite to the voltage of the secondary winding of said transformer at no load on said motor for vectorially combining with the voltage of the transformer secondary winding to provide a resultant voltage which increases with increase in the net load on the motor; a rectifier; a condenser connected with said rectifier in series therewith to be subject to said combined voltages so that upon each operation of said car said condenser is charged with unidirectional current in accordance with the load on the motor; an electromechanical brake for said motor; a circuit for supplying current to the release coil of said brake; a discharge resistance for said brake release coil; a switch having an operating coil connected in parallel with said condenser to be operated upon each operation of said car and having contacts which when the switch is operated connect said discharge resistance across said brake release coil; and switching mechanism operable at a fixed distance from any of said landings at which a stop is to be made to break the circuits for said motor and brake release coil and to discontinue the charging of said condenser whereupon said condenser discharges into said switch coil to maintain the switch operated and thus the discharge resistance connected across the brake release coils to maintain the brake released for a time determined by the load on the motor, whereby the brake is applied at a distance from the landing at which the stop is being made to compensate for the load in the car.

11. Load compensating apparatus for an elevator installation in which the elevator car serves a plurality of landings and is driven by a threephase alternating current induction hoisting motor which is connected to a source of three-phase alternating current for starting and disconnected therefrom for stopping, said apparatus comprising; a single phase current transformer having its primary winding connected in one of the alternating current supply lines in series with said motor and one side of its secondary winding connected to a second of said supply lines; a voltage divider resistance connected between said second supply line and the remaining supply line and having an adjustable point thereon for providing a voltage from said second supply line to said adjustable point for combining with said secondary voltage; an adjustable loading resistance connected across said secondary winding, said voltage divider resistance and said loading resistance being adjusted so that said secondary voltage and said fixed voltage which is combined therewith are substantially equal and 14 opposite at no load on said motor; a rectifier; a condenser connected across the other side of said secondary winding and said adjustable point with said rectifier in series therewith so that upon each operation of said car said condenser is charged with unidirectional current in accordance with the load on the motor; an electromechanical brake for said motor; a circuit for supplying current to the release coil of said brake; a discharge resistance for said brake release coil; a switch having an operating coil connected in parallel with said condenser to be operated upon each operation of said car and having contacts which when the switch is operated connect said discharge resistance across said brake release coil; and switching mechanism operable at a fixed distance from any of said landings at which a stop is to be made to break the circuits for said motor and brake release coil and to discontinue the charging of said condenser whereupon said condenser discharges into said switch coil to maintain the switch operated and thus the discharge resistance connected across the brake release coil to maintain the brake released for a time determined by the amount of charge on the condenser, in turn determined by the load on the motor, whereby the brake is applied at a distance from the landing at which the stop is being made to compensate for the load in the car to bring the car to an accurate stop.

ANTHONY PINTO.

No references cited. 

